The present invention relates to a device for releasably securing stationarily a finely angularly adjusted shaft in an instrument with respect to the body thereof, and, more particularly, to a device for releasably securing a finely angularly adjusted shaft in an instrument connected to components required to be finely adjusted their operating positions and a coaxial tubular shaft fixedly secured to the above described shaft and connected to indicating means for indicating the adjusted positions of the shaft with respect to the body of the instrument.
The device of the type described above was well known in the art.
Such a well known device comprises a core shaft rotatably supported in a body of the instrument and operatively connected to components such as a movable contact of a potentiometer or a rotatable pole plates of a variable capacitor for turning purpose of a short-wave radio communication system requiring fine adjustment and a coaxial tubular shaft fixedly secured around the core shaft and connected to indicating means, preferably, to digital indicating means for indicating the adjusted position of the shafts. The tubular shaft is journaled in a cylindrical flange extending upwardly from the upper wall of the body of the instrument. The cylindrical flange is formed with a plurality of cut-out portions circumferentially spaced from each other. A rotatable clamping ring is rotatably fitted around the tubular flange and it is formed with the same number of wedge-shaped recesses in the inner periphery thereof as the number of the cut-out portions along the inner periphery thereof circumferentially spaced from each other, the relative positions of the recesses to each other corresponding to the relative positions of the cut-out portions to each other. A clamping member such as a roller is located in each of the recesses and the cut-out portion positioned in alignment therewith. Thus, when the clamping ring is rotated in one direction around the cylindrical flange after the shafts are finely adjusted their angular positions, each of the clamping members is urged radially inwardly by the wedge-shaped recess during the rotation of the clamping ring so that the clamping members are pressed against the tubular shaft so as to stationarily secure the shafts with respect to the body of the instrument, while, when the clamping ring is rotated in the opposite direction, the clamping members are permitted to be released from the tubular shaft so that the shafts can be freely rotated for the readjustment.
In such a device described above, the clamping members are necessarily rotated within the cut-out portions when the clamping ring is rotated in the direction for securing the shafts even though the clearance between the cut-out portion and the clamping member is made to the minimum. Therefore, it can not be avoided that the rotation of the clamping members causes the rotation of the tubular shaft at the moment the same is to be stationarily secured by the rotation of the clamping ring, thereby resulting in fatal disadvantage that the shafts can not be accurately secured at the desired value of the indication given in the indicating means because the shafts are rotated from the finely angularly adjusted positions just at the moment they are secured by the rotation of the clamping ring causing the rotation of the clamping members.